Standardizing radon sensor units

[Kirchoff]

As requested from @bdraco, I'd like to propose a discussion on how to handle making radon measuring sensors a standard. My PR that prompted this discussion is located here: #103709

My personal interest in this topic is that I recently added an AirThings View Plus air quality monitor to my home. While I can view the radon measurements in the AirThings app with either SI (Bq/m^3) or Imperial (pCi/L) units, the Home Assistant integration defaults to SI. It also does not support viewing those sensors in Imperial units. I noticed that there are a total of 3 existing components that measure/display radon, and all 3 do it quite differently. This PR was an attempt to standardize.

Please let me know if I can add anything further. Thanks.

[jpbede]

Isn't this a duplicate of #886?

[Kirchoff]

It sure looks like it is, my apologies for missing that.

[bdraco]

@Kirchoff It would be good to comment on that discussion with any thoughts as it seems a bit stalled due to lack of interest. I suspect the number of people who are experts on radiation measurements is a small group which makes it a bit more difficult to arrive at a conclusion. These type of discussions can take a long time because its very hard to change later if we get it wrong.